Humic acids comprise various organic acids obtained from humate, a complex variable material resulting from partial decomposition over time of plant or animal matter and forming the organic portion of soil. The natural process of forming humate involves the biological breakdown of organic materials over extended periods of time to form organic colloids and humic acids. During this natural process, various available plant nutrients are attached to the humic acid molecules and absorbed into the organic colloids to form complex molecular clusters of humic acids and humic salts of plant nutrients. The resulting fertilizer is stable and efficient in providing nutrients to the plant and is substantially more stable than common chemical fertilizer forms, but the formation of naturally forming humic acid fertilizers takes long periods of time for natural production.
Until approximately the turn of the century, waste organic materials were used extensively as a primary nitrogen source of fertilizers. Today, even though waste organic materials such as agriculture wastes, agroindustrial processing wastes, and solid and liquid municipal waste are available in great quantities, such materials represent a small fraction of the total fertilizer market, with chemical fertilizers furnishing the majority of the fertilizer demand, primarily because no commercially viable method and apparatus have been developed for economically converting these waste organic materials to useable form as fertilizer having a high nitrogen content and providing controlled release of nutrients for plant growth.
Combining treated organic waste with inorganic materials to form a useful fertilizer is described in applicant's U.S. Pat. No. 4,743,287. Other prior art methods for making fertilizer are described in U.S. Pat. No. 3,050,383 to Wilson; U.S. Pat. No. 3,966,450 to O'Neil; U.S. Pat. No. 3,929,446 to Trocino; and U.S. Pat. No. 3,942,970 to O'Donnell.
The method for making fertilizer described in applicant's U.S. Pat. No. 4,743,287 includes the use of a pressure reactor vessel. This pressure reactor vessel can be expensive to manufacture and maintain operational and it is difficult to maintain pressure seals where the process material enters and exits the pressure vessel.
In other methods for making organic material based fertilizer, applicant has employed a process wherein a mixture of organic material and inorganics including phosphate, potash and trace minerals were placed in a mixer and a quantity of sulfuric acid was added to that mixture. A forty minute curing step followed the addition of acid. The cured mixture was then returned to the mixer wherein ammonia was added in sufficient quantity to produce a fertilizer of the desired pH. This process proved commercially impractical because it resulted in the generation of large quantities of fumes and heat during the addition of ammonia to the mixture, resulting inefficient use of the ammonia and generation of volatile fumes.